1. Field of the Invention
The present invention relates to phosphonium salts and processes for production of and uses for the same and, further, to phosphines deriving the same and processes for producing said phosphines.
The phosphonium salts provided by the present invention are useful as components of catalysts accelerating telomerization of a conjugated diene and an active hydrogen compound. Accordingly, the above uses include telomerization catalysts comprising the phosphonium salts provided by the present invention and, also, processes with use of the telomerization catalysts for producing alkadienyl compounds. The alkadienyl compounds obtained by the telomerization, such as 2,7-octadien-1-ol, 1,7-octadien-3-ol, 1-acetoxy-2,7-octadiene and 1-amino-2,7-octadiene are usable, for example, as starting materials for various polymers, medicines, agricultural chemicals and the like.
2. Description of the Related Art
U.S. Pat. No. 4,142,060 and GB1553002 disclose telomerization of dienes in the presence of a catalyst comprising a water-soluble phosphine and a palladium compound. Known water-soluble phosphines include the quaternary ammonium salts of (sulfophenyl)diphenylphosphine, di(sulfophenyl)phenylphosphine or tri(sulfophenyl)phosphine. Of these phosphines, the tetraethylammonium salt of tri(3-sulfophenyl)phosphine containing 60% of trivalent phosphorus is actually used for telomerization of butadiene. Such a tetraethylammonium salt of tri(3-sulfophenyl)phosphine contains an impurity of pentavalent phosphorus. According to a study by the present inventors, use of a phosphine containing a large amount of an impurity of pentavalent phosphorus, as a constituent of a telomerization catalyst, leads to accumulation of impurities in the reaction mixture, thereby changing the solubility of the reaction substrates and exerting similar bad influences on the reaction.
“Applied Catalysis A: General”, 131(1995) 167–178 describes use of the dimethyldodecylamine salt of diphenylphosphinobenzene-3-monosulfonic acid (water-insoluble), which has a surface-active property, for telomerization of butadiene. However, this reaction has a low rate.
U.S. Pat. No. 4,716,250 and EP0254937B1 disclose the higher amine salts, such as trioctylammonium salt, dimethyloctylammonium salt and dimethyldodecylammonium salt, of diphenylphosphinobenzene-3-sulfonic acid as ligands for hydroformylation catalysts. U.S. Pat. No. 5,663,426 and EP0704450B1 disclose sulfonated phosphines as constituents of water-soluble catalyst systems for C—C bond forming reactions such as hydroformylation. These patents describe, concretely, the steps of sulfonating a phosphine in a mixed liquid comprising fuming sulfuric acid, boric acid and concentrated sulfuric acid, treating the sulfonated product with a solution of triisooctylamine in toluene, to obtain the triisooctylamine salt of the sulfonated phosphine, introducing the salt into an organic phase, and subjecting the resulting organic phase to extraction with an aqueous sodium hydroxide solution, to obtain the sodium salt of the sulfonated phoshine. These higher amine salts of sulfonated phosfines are insoluble in water and hence cannot provide commercially advantageous telomerization catalysts.
It is known, generally, with catalysts comprising a phosphine and a transition metal, that while a large amount of the phosphine realizes good stability of the resulting catalyst, which has, however, an insufficient catalytic activity, a small amount of the phosphine leads to poor stability of the catalyst, which cannot exert the catalytic activity continuously. The catalytic activity and the stability are thus incompatible with each other, which renders it impossible, with use of a catalyst comprising a phosphine, to produce alkadienyl compound commercially advantageously.
In order to solve the above problems, Japanese Patent No. 2635519, U.S. Pat. No. 4,927,960, U.S. Pat. No. 4,992,609, U.S. Pat. No. 5,100,854 and EP0296550B1 disclose a process for carrying out telomerization with use of a catalyst comprising a phosphonium salt and a palladium compound. For instance, telomerization of a conjugated alkadiene and water is carried out with use of a catalyst comprising a water-soluble phosphonium salt containing a group of the formula —SO3M or —COOM (wherein M represents an alkali metal such as lithium, potassium or sodium) and a palladium compound, in the presence of a mixed solvent of sulfolane and water and under a pressure of carbon dioxide.
The present inventors made a test run of dimerization of butadiene and water with use of a telomerization catalyst comprising a phosphonium salt derived from an alkali metal salt of diphenylphosphinobenzene-3-monosulfonic acid and a palladium compound, continuously over a long period of time, to find occasional formation of precipitates in the reaction zone, which caused clogging of the piping and decreased the heat conduction efficiency of the reactor.
As a result of an intensive study to clarify the mechanism involved in the precipitation, the present inventors have found that, on dimerizing butadiene and water continuously over a long period of time, the concentration of the alkali metal ion constituting the phosphonium salt in the reaction mixture increases to an unexpected level, that the alkali metal ion reacts with a reaction accelerator of hydrogencarbonate ion or carbonate ion to form the alkali metal hydrogencarbonate and/or alkali metal carbonate, which precipitates in the reaction mixture. These phenomena were quite unexpected, because, originally, alkali metal hydrogencarbonates and alkali metal carbonates maintain the state of solution under the conditions of dimerization of butadiene and water.